Product engineering is an interdisciplinary discipline, at the crossroads of process engineering, material science and product-consumer interaction. Three examples relevant to food and FMCG are presented, to highlight how product engineering presents interesting challenges involving Interfacial Science, Transport Phenomena and Rheology.

The wetting, dispersion of dehydrated food and FMCG powders condition strongly the dissolution performance upon rehydration. The wetting and dispersion of grains at an air-liquid interface were studied to highlight the conditions leading to wicking into the powder pores [1,2] or conversely leading to the formation of undesired lumps. Importantly, it was observed that introducing flow in the liquid by agitation does not necessarily improve the dispersion process. The wetting of a soluble coating was also studied, highlighting the interplay between moisture transfer and wetting [3] and the effect of the physico-chemical properties of the substrate on the contact line dynamics [4].

Dip coating, widely used in food manufacturing, is considered as a second example. Controlling the thickness of a coating (e.g. chocolate) is key to deliver the desired sensorial properties and to be compliant with the product’s nutritional claims. The complex rheology of most food products makes the process difficult to design and reduces the coating homogeneity. Upon coating a flat plate using Hershel-Bulkley fluid, the final average coated thickness is always significantly lower than the critical thickness that can be predicted from the liquid density and yield stress. The impact of yield stress and withdrawal speed on the average coating thickness and its uniformity is discussed [5], considering also repeated dipping. The results are interpreted in the context of the existing theories.

The design of thickeners to manage swallowing disorders is presented as a last example. Swallowing disorders result in a significant deterioration of the quality of life and can be life-threatening. An in vitro experiment replicating the sagittal section of the oral cavity was developed and compared against in vivo data. The in vitro model was used to better understand the effect of the rheology of the bolus on its dynamics and to compare contrast agents used to diagnose dysphagia with thickeners used to manage swallowing disorders [6,7].